This research aims to apply recent technological advances in analytical biochemistry to delineation of the compositional and physicochemical properties of selected human liver metalloenzymes. Both the catalytic features of the protein moiety and the reactivity of its essential metal ion serve as guides for the progressive purification of each metalloenzyme and as sensitive indicators of chemical interactions with smaller molecules, such as kinetic inhibitors or chromophoric metal chelates. Alcohol dehydrogenase, glutamate dehydrogenase, monoamine oxidase, xanthine oxidase, and pyruvate decarboxylase are to be isolated. The chemical characterization of each of these presumed metalloenzymes will include determination of specifc absorbance, metal content, molecular weight, amino acid composition and end-group analysis, and electronic (absorption, circular dichroic and EPR spectra) and kinetic properties. Next, the conditions for their equilibrium metal isotope exchange reactions will be delineated both in the presence and absence of added coenzymes, substrates, inorganic ions, and larger organic and polypeptide species. These studies will provide unique information describing the functional properties of human liver metalloenzymes involved in the biochemical alterations attending ethanol metabolism. In addition, the metal isotope exchange studies may be anticipated to provide a basis for development of new, highly selective means for imaging of the human liver by external radiation detectors.